Not applicable.
Not applicable.
The preferred embodiments of the present invention generally relate to a x-ray detector for a x-ray imaging system and a method of manufacturing the detector.
X-ray imaging systems are used, for example, for medical application in diagnosing and treating patients. A x-ray system comprises a x-ray source, the rays from which are partially absorbed by the object being imaged, e.g., a patient, and a x-ray detector. The x-ray detector comprises a x-ray imager which absorbs x-rays and creates an electrical signal related to the number of x-rays absorbed across an area. External circuitry controls the x-ray imager and reads out the imager""s signals and mechanical housing. The x-ray system may also comprise computers to control the system and store data and mechanical gantries and tables to position the various elements.
The x-ray imager further includes a light imaging array formed on a substrate, a scintillator, and a cover plate. The x-rays enter the x-ray imager through the cover plate and are absorbed by the scintillator. The scintillator then converts the x-rays into light and emits the light onto a light imaging array which contains numerous light sensitive elements or pixels. The pixels comprise photosensitive elements, such as photodiodes, the signal from which is read out via contact fingers outside the light imaging array to contact pads located near the perimeter of the substrate. External circuitry is connected to the contact pads which in turn process the signals into a readable image.
Since the light imaging array is sensitive to light, it must be shielded from all ambient light. Also, the scintillator""s performance is effected by the absorption of moisture (hygroscopic), and must be protected from ambient moisture. Therefore, the x-ray imager contains a moisture-resistant, opaque cover plate which lies over, but does not come into contact with, the scintillator or the imager substrate. The cover plate is affixed to the substrate using a sealant such as epoxy. The epoxy seal extends around the entire perimeter of the cover plate, thus completely enclosing the light imaging array and scintillator. Conventional detectors have experienced certain drawbacks in manufacturing and operation as the cover plate is placed over the imaging array and scintillator (hereafter referred to as the sealed cavity). The cover plate compresses the epoxy, causing the epoxy to flatten and spread laterally, which enhances the contact between the epoxy and both the substrate and the cover plate. Furthermore, once the seal is initiated between the substrate, the cover plate and the epoxy, the compression of the epoxy increases the pressure within the enclosed sealed cavity, often causing non-uniform, outward lateral expansion of the epoxy. Oftentimes, the expansion causes the seal to fail because 1) the seal becomes too narrow in local regions to effectively protect against light or moisture from entering the sealed cavity and/or 2) the epoxy expands outward to the contact pads, thereby greatly reducing the ability to make contact with external circuitry.
The preferred embodiments of the present invention address these needs and other concerns.
A preferred embodiment of the present invention includes an apparatus and method for sealing an imaging detector. One preferred embodiment of the present invention seals a x-ray detector that includes a light imaging array, a substrate, a scintillator, and a cover plate. The cover plate, scintillator, and substrate define a cavity. A bead of epoxy or other sealant is placed around the sealed cavity, preferably on the substrate. However, the epoxy does not extend completely around the entire region; rather, a small pressure opening or gap remains. It is preferred that the pressure opening is located near one comer of the sealed cavity. When the cover plate begins to compress the epoxy, any build-up of pressure within the sealed cavity escapes through the pressure opening. Thus, the use of a pressure opening leads to a reduction in the outward pressure on the epoxy, which in turn reduces the outward lateral expansion of the epoxy. After the cover plate is attached, the pressure opening is filled with epoxy through the use of a soft-tipped syringe, thereby enclosing the sealed cavity.
Alternatively, a preferred embodiment of the present invention may include multiple pressure openings that may be located at any point around the perimeter of the sealed cavity. Although it is preferred that the same substance is used as the sealant and the gap sealant, an alternative embodiment may utilize different substances for each. Another alternative embodiment may fill the pressure opening by using a metal-tipped syringe if the tip is properly angled to allow insertion of the tip into the pressure opening without making contact with either the scintillator or light imaging array.
These and other features of the present invention are discussed in the following detailed description of the preferred embodiments of the present invention. It shall be understood that other features and advantages will become apparent to those skilled in the art upon review of the following detailed description, drawings, and claims.